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GB 2 question...


Rimshot

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I was looking thru some customer reviews about the GB2 when I ran across this statement.

"As knowledge increases using this detector you will learn that the circuitry will block out lead etc that could hide gold."

Now to me this contradicts everything I have read here as well as other places.

I thought Gold and Lead mimic each other.

Me confused.

Rim

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My first detector was a GB2 and I disagree with that statement. If you were to ground balance over a piece of lead then the statement might be true. I would really question the author of the statement. The GB2 is a good basic machine for it's price. Ed Coogan, a long time detectorist help develop the GB2. One of the things he taught me was that if I got into mineralized ground was to reground balance on that ground to help eliminate the influence of it mineralization, however, the down side was that you would miss some targets as a result of it. Jerry

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My first detector was a GB2 and I disagree with that statement. If you were to ground balance over a piece of lead then the statement might be true. I would really question the author of the statement. The GB2 is a good basic machine for it's price. Ed Coogan, a long time detectorist help develop the GB2. One of the things he taught me was that if I got into mineralized ground was to reground balance on that ground to help eliminate the influence of it mineralization, however, the down side was that you would miss some targets as a result of it. Jerry

Jerry,

Does Gold and Lead have the same tones on a metal detector? Or is there a small bit of difference in the sound?

And thank's for your reply!

Rim

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Thank you all for confirming what I thought I had learned...I sure wish the gb2 had a nice lcd screen but then that would just add more weight.

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I had a gb and the gb-2...I have no clue why anyone would say or write that...I doubt it is even possible, unless the new models have some way different circuitry...

perhaps you misread? I have dug gold and lead out of the very same place and could not know which it was until I had it in hand,,,

fred

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Well Frank this is kinda why I like screens. uuummm.....

Three retirees, each with a hearing loss, were taking a walk one fine March day.

One remarked to the other, "Windy, ain't it?"

"No," the second man replied, "It's Thursday."

And the third man chimed in, "So am I. Let's have a coke." :ROFL:

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My experience with my GB2 is that I can tell the difference between birdshot and tiny dinks reliably ... The birdshot has a slight crackle at the end of the signal ... Not so reliable though on anything over about a quarter gram ... Cheers, Unc

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My experience with my GB2 is that I can tell the difference between birdshot and tiny dinks reliably ... The birdshot has a slight crackle at the end of the signal ... Not so reliable though on anything over about a quarter gram ... Cheers, Unc

Thank's Ron!

Might be due to the 71khz factor. But this is the kinda info a rookie would definitely want to know.

Just curious Ron...Have you found any big nugs with it? If so, how deep? And was the ground highly mineralized?

Rim

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My biggest with the GB2 was about 3 DWT ... The deepest, about 2.5 DWT was about 16" with 10" coil ... Surface to about 8" was the average and I found lots of .5 to 2 DWT nuggets at that level, and hundreds of dinks below 1/4 gram at surface to 3" ... I still use it when I just have to get my nugget bone rubbed out of hammered patches ... Cheers, Unc

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Rim, I am curious where you read that statement.

Now, one might mix things up a little and that just might be what happened by meaning it is possible to use lead as a suitable target for gold and when testing with lead, one will learn there will be hotrocks that will cause a lead target to be ignored.

This condition happens easily on any VLF. Simply ground balance to typical normal ground and take a piece of magnetite maybe the size of a golf ball and place a piece of lead such as a lead bullet or even a gold nugget up to a half oz next to or under the magnetite rock and you will see how easily the magnetite causes the gold to be missed.

The reason is simple, the signal from the magnetite is a multitude times stronger than the signal from gold, thus even a large piece of gold can be ignored.

Fortunately, the GB 2 doesn't suffer nearly as bad from this condition as most other nuggethunting VLF detectors.

BTW, I used to use this demo when discussing why ground balancing is very important. My test object was a half oz nugget I found at Rich Hill and the magnetite was a golf ball size black hotrock I picked up years before here in Colorado. I would take the nugget and display how well I could detect it. I then would take a bag of plain dirt and ground balance the detector to the dirt. I then took the nugget and the dirt and displayed how I could detect the nugget through the dirt. At this ground balance setting all VLF's tested failed to detect the nugget when I combined with the rock and passed them by the coil The VLF's tested included the GB 2, plus a bunch of other gold detectors such as the XT18000, the Lobo, A Whites Goldmaster, and a few other detectors I had at the time.

A while back I demonstrated to a GB 2 owner how easily a simple granite rock with some magnetite in it could easily cause a small nugget to be ignored. All I had to do was to have the rock produce a slight but obvious negative response when passed over with the coil. This can be easily done by adjusting the ground balance. At this setting, a small nugget placed next to under the rock would easily cause the nugget to be ignored.

Anyway, it is something to test.

One final note and that is, lead can be substituted for gold, but brass is a little more accurate in mimicking gold. Usually, lead is much less conductive than gold, but when the chemistry is right, meaning the gold is alloyed with a higher silver or copper content, it is possible that the gold will have a reduced conductance that is closer to gold.

How wide of a range does the gold vary? Well, a half oz nugget found at Rich Hill was very conductive because of the high purity. Another nugget found a few miles from Rich HIll displayed quite a different response and reacted like a much lower conductive metal.

Near pure gold can be mimicked by using something like an aluminum ingot.

For those interested, here is a link to a site that displays how the conductivity of gold can vary. If you look at the chart at this site, one column is conductivity and you will notice that pure gold has a rating of 77 while gold heavily alloyed with silver can have a conductivity rating as low as 10.

http://www.deringern...dGoldAlloys.asp

Another chart at this website displays most metals and their conductivity.

http://www.eddy-curr...com/condres.htm

There are some variations as to exact conductivities of each metal but the variations are minor with copper being the baseline of 100 and all other metals displayed as they relate to it.

Sorry to be so long winded, but when I get started, it is hard to quit. Fortunately, readers have the option to quit reading if it becomes boring.

Reg

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Reg ... Excellent post. I am going to keep both of those charts with my instruction props ... most student detectorists I find don't know how close lead sounds to gold and vise versa ... and almost all want to know how they can tell gold is not lead and vise versa so they don't have to waste time digging all that lead. I tell them dig it all ... or in lieu of that ... give me the gps co-ords of the target they don't want to dig and I'll go dig up the missed gold! :) I do say that tongue in check of course ... most then say OK I'll dig it all! Lesson learned.

Mike F

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Rim, I am curious where you read that statement.

Now, one might mix things up a little and that just might be what happened by meaning it is possible to use lead as a suitable target for gold and when testing with lead, one will learn there will be hotrocks that will cause a lead target to be ignored.

This condition happens easily on any VLF. Simply ground balance to typical normal ground and take a piece of magnetite maybe the size of a golf ball and place a piece of lead such as a lead bullet or even a gold nugget up to a half oz next to or under the magnetite rock and you will see how easily the magnetite causes the gold to be missed.

The reason is simple, the signal from the magnetite is a multitude times stronger than the signal from gold, thus even a large piece of gold can be ignored.

Fortunately, the GB 2 doesn't suffer nearly as bad from this condition as most other nuggethunting VLF detectors.

BTW, I used to use this demo when discussing why ground balancing is very important. My test object was a half oz nugget I found at Rich Hill and the magnetite was a golf ball size black hotrock I picked up years before here in Colorado. I would take the nugget and display how well I could detect it. I then would take a bag of plain dirt and ground balance the detector to the dirt. I then took the nugget and the dirt and displayed how I could detect the nugget through the dirt. At this ground balance setting all VLF's tested failed to detect the nugget when I combined with the rock and passed them by the coil The VLF's tested included the GB 2, plus a bunch of other gold detectors such as the XT18000, the Lobo, A Whites Goldmaster, and a few other detectors I had at the time.

A while back I demonstrated to a GB 2 owner how easily a simple granite rock with some magnetite in it could easily cause a small nugget to be ignored. All I had to do was to have the rock produce a slight but obvious negative response when passed over with the coil. This can be easily done by adjusting the ground balance. At this setting, a small nugget placed next to under the rock would easily cause the nugget to be ignored.

Anyway, it is something to test.

One final note and that is, lead can be substituted for gold, but brass is a little more accurate in mimicking gold. Usually, lead is much less conductive than gold, but when the chemistry is right, meaning the gold is alloyed with a higher silver or copper content, it is possible that the gold will have a reduced conductance that is closer to gold.

How wide of a range does the gold vary? Well, a half oz nugget found at Rich Hill was very conductive because of the high purity. Another nugget found a few miles from Rich HIll displayed quite a different response and reacted like a much lower conductive metal.

Near pure gold can be mimicked by using something like an aluminum ingot.

For those interested, here is a link to a site that displays how the conductivity of gold can vary. If you look at the chart at this site, one column is conductivity and you will notice that pure gold has a rating of 77 while gold heavily alloyed with silver can have a conductivity rating as low as 10.

http://www.deringern...dGoldAlloys.asp

Another chart at this website displays most metals and their conductivity.

http://www.eddy-curr...com/condres.htm

There are some variations as to exact conductivities of each metal but the variations are minor with copper being the baseline of 100 and all other metals displayed as they relate to it.

Sorry to be so long winded, but when I get started, it is hard to quit. Fortunately, readers have the option to quit reading if it becomes boring.

Reg

Hi Reg,

I read that review on a site that sells metal detectors. Out of respect for Bill (since he is also in the business of selling detectors) I wouldn't want to post a link that would lead to a competitor's site. That's why I didn't provide a link to the review.

I would like to see a real test between the Valquero vs. GB2 vs. Minelab Extera 705. I wonder which one would win the best overall VLF detector award. lol!

TEST

A) Find a pro operator for each detector. Put them on a 1 acre (gold producing) tract which is divided into 3 equal sections.

B) Allow them to detect each section for a period of 2 hours. So the total test will run a total of 6 hours for each detectorist.

C) Weigh each pros gold at the end of test to determine which detector did the best.

* All 3 pros would have to determine which coil they will use before the 6 hour test begins.

Now that to me is a test... :rolleyes: Well it's the right test for me to make a decision on as to which detector I would buy.

Rim

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Rim ... Only problem I see with that is the GB2 and 705 operators ... not familiar enough with the Vaquero to comment ... would clean up the two sites they were on leaving little for the successive tests. And then you would have to somehow insure there were equal values of targets on each site. Does that make sense?

A better test might be to have each pro with their respective machines find and flag targets on one of the 3 fields. Then after a two hour period all three pros visit all targets found and flagged to see if the other pros can hear the target. A point would then be awarded to the pro who could NOT hear the target ... the pro with the most points at the end of the inspection of all flagged targets on all 3 fields is the loser ... the one with the fewest is the winner. In the case of the finder pro being the only one to hear a flagged target ... that target will be dug to prove that a target did indeed exist. Failing to recover the target in that case will result in removal of the point assigned to those not hearing the 'target'. What do you think about that for a test.

Mike F

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Rim ... Only problem I see with that is the GB2 and 705 operators ... not familiar enough with the Vaquero to comment ... would clean up the two sites they were on leaving little for the successive tests. And then you would have to somehow insure there were equal values of targets on each site. Does that make sense?

A better test might be to have each pro with their respective machines find and flag targets on one of the 3 fields. Then after a two hour period all three pros visit all targets found and flagged to see if the other pros can hear the target. A point would then be awarded to the pro who could NOT hear the target ... the pro with the most points at the end of the inspection of all flagged targets on all 3 fields is the loser ... the one with the fewest is the winner. In the case of the finder pro being the only one to hear a flagged target ... that target will be dug to prove that a target did indeed exist. Failing to recover the target in that case will result in removal of the point assigned to those not hearing the 'target'. What do you think about that for a test.

Mike F

Mike,

I think that's a dandy of an idea!

And yep I thought about the pro that got the luck of the draw to get the section with the most gold on it to start on. But that doesn't necessarily mean that he will find the most gold on that section. Is two hours enough time to thoroughly search 1/3 acre? I guess it depends on how many trash targets he digs. Oh! And I forgot to add in the bone factor. All 3 pro's need to be young, healthy and energetic.

I like both test idea's Mike!

Rim

PS- If ya'll could get a few sponsers to put up a little cash this would be a fun game to play on some of your outings. Maybe have different classes in the event's like PI and VLF classes, amateur and pro, or even partners event's for that matter. Sounds like fun and who knows but maybe it's already been tried. I don't know because i'm just rookie. :hahaha:

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My biggest with the GB2 was about 3 DWT ... The deepest, about 2.5 DWT was about 16" with 10" coil ... Surface to about 8" was the average and I found lots of .5 to 2 DWT nuggets at that level, and hundreds of dinks below 1/4 gram at surface to 3" ... I still use it when I just have to get my nugget bone rubbed out of hammered patches ... Cheers, Unc

Wow Ron!

And not even a quarter ouncer? How long you been using that detector? I was hoping you would say at least a 1/2 ouncer... :tisk-tisk:

But thank's for the responce.

I got to quit dreamin about muffins nuggets....sheeeeshhhhhhh!!!! :hahaha:

Rim

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I began using the GB2 in 1994 ... I started with a White's GMT in 2000 and began finding larger nuggets with it, up to a little over a half ounce ... I didn't start finding larger, deeper nuggets until I switched to my ML SD2100 in 2001 ... Have found many bigger nuggets, including some over an ounce ... Now I use the ML GP 4500 and have lots of smaller nuggets in old hammered patches and a few between 1/4 and 1 oz. ... Still use the GB2 and GMT in dink patches ... Cheers, Unc

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Ron,

Were you prospecting the same locations all of this time? Just trying to rule out any other factors that might have changed the size of the nugget's you were finding.

Rim

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Ron,

Do you think it would have helped in regards to larger nugget's being found if you had of been using one of the less expensive gold bugs running in lower khz range? That's my final question.

Thank's!

Rim

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The GB2 is a great gold finding detector when in the hands of someone who knows how to put it to best uses. The topic of "how best to use a GB2" defies easy simplifications. This is so because of the complexities of the ground -- not the detector. Therefore, the "general rules" have many exceptions [or, at least, exceptional situations]. A few examples:

1. Dealing with iron rich ground. A general rule is that the high frequency of the GB2 reduces its ability to penetrate iron rich or heavily mineralized soils [often meaning the dirt itself as opposed to gravels]. This is a true statement, but that doesn't mean the GB2 is useless -- the dirt simply absorbs the signal and limits a GB2 depth wise. There are some gold patches that are very near the surface and, thus, the gold is within range of the GB2. The use of a surface soil scraping tool is a way of dealing with this situation [getting the gold close enough to be detectable]. Another solution is to switch to a lower frequency detector, recognizing the limits of your machine.

2. Coping with magnetite: There are places where magnetite-type hot rocks litter the surface -- and sometimes the subsurface, too. The general rule in such a situation is to ground balance a GB2 slightly negative. Once this is done the GB2 becomes very noisy. But that's okay for my ear because the great majority of the hot rocks begin making "boing, boing, boing" sounds while the gold [and lead, tinfoil, brass, etc.] still goes "zip, zip, zip". An exception exists. Such hot rocks can vary in the percentage of Fe3 04 content. Thus, some will not go "boing, boing" until the ground balance is adjusted considerably more negative. Another exception includes magnetite that ALSO contains a dose of Ag or Cu or other highly conductive alloy. These exceptions sometimes can be dealt with by the GB2 operator simply by having a strong magnet to pick up certain of the super-hot rocks [as well as another common nemesis -- tiny, barely visible slivers of wire screen]. Another solution might be simply to kick the offending stone out of the way.

3. Coping with graphite: Another challenge to a GB2 operator is graphite [a form of elemental carbon]. Graphite can be fine grained and shot throughout certain types of host rock. It is highly conductive and thus results in a zippy response. These types of stones create special difficulties that a GB2 was not designed to deal with. Compared to a piece of gold, the more diluted graphite bearing stones lose their "halo" a short distance removed from a search coil. Thus, just raising a GB2 coil up somewhat higher can help. Switching to "Iron Discriminate" may help, but it is not reliable. Also, hefting the stone usually reveals it to be extremely light. Unfortunately, graphite also can be present in lumps. Hardrock mine tailing piles often contain chunks of quartz that will give the sweetest kind of zippy signal a GB2 operator dreams about hearing. But after breaking open the specimen, the "hidden gold" turns out to be just a blackish little knot of graphite. There is no GB2 trick I know of to eliminate such an ambiguity. This is an instance of knowing the limitations of your machine. Switching to "Iron Discriminate" its useless because the graphite will cause a GB2 to chirp, chirp, chirp very loudly and with much gusto. However, a different type of unit such as a pulse induction probe typically will ignore such a specimen.

Bottom line: Prospectors are tool users and must understand what each of their tools can and cannot do. They must be able to recognize and adapt to different conditions. This is the single most important factor in determining whether a prospector will regularly recover gold. No machine ever will be invented to take the place of the long hours of trial and error that go into transforming a novice into a journeyman.

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Hi Jack,

I never tried to use an ohmmeter to check the gold content, so I can't say for sure. However, my best guess woule be no, meaning one can't tell with any real accuracy the gold content. However, if done right, it might indicate some generallities.

One might use a TID (Target ID) type metal detector and then you would have to have a baseline from which to work. On a coin machine with TID, the readout indicators already display that two objects with identical chemistries will have different readings. This is displayed by noting that silver coins vary in conductivity indication by their size. The same would hold true for gold nuggets. So, one might get an idea of the difference between nuggets from different areas that are very close to the same in size.

Thus, what one can determine would be general concepts such as a small gold nugget will normally read less on the meter than a larger piece of gold from the same vein or location. Thee is no doubt that the chemistry or purity will also do the same.

Remember, size, shape, purity, surface characteristics and contiguous connections in the case of specimens all will factor in on how a gold nugget will respond. On a VLF with metering capabilities, this means how it will read on a digital or analog readout. On a PI, it also means how the nugget will respond with a high/low or low/high tone, or in the case of the TDI rather the nugget will indicate a high tone or a low tone.

Now, on the ML's, the settings or program selected can also alter the indications, so this isn't quite as forward as one might think. Even the tone indications can change by simply altering the delay or the ground balance setting. So, the TDI sort of shows you something as to what might really be happening on the ML if one were to analyze a target or two and compare the results by going through all the timings, etc, on the ML and then comparing similar results to what one gets with a TDI at different settings.

Since the ground balance technique is limited on a PI, meaning one can vary cerain factors, other factors have to be fundamentally the same. What this means is when changing programs, one is changing one or more of the following, pulse length, delay setting, relationship between the main sample and the secondary sample, and finally, the other filtering that has an influence.

What is important to remember is not so much what is changed, but how a certain timing or program setting affects the target response across a band of targets. This will show how some targets are high/low tones and others are low/high tones and how they change with a different setting. Knowing this will help the operator better understand what the target might be. Unfortunately, the gold characteristics mentioned before can change any standard results one might run on a series of nuggets from different locations. Thus, this idea as a form of tecting can get complicated in a hurry.

Actually, it isn't as complicated as it might appear once a person realizes that knowing more about the gold from a location has an effect and what that effect might be.

For me, this is a simple but very important principal. As an example, in one location here in Colorado, a large nugget will normally read as a high tone on my TDI even if it is an ounce or more, while a similar size nugget found at or near Rich Hill will read a strong low tone. So, I can change my settings accordingly to maximize my ability to find the gold by size if I know what to expect. This is further a benefit because ferrous objects also have a level of predictablility, meaning I can separate the gold from the iron junk, thus reducing the targets I need to dig.

I suspect this can be also done with the ML once a person has a good handle on target responses of both gold and ferrous junk in the various modes, programs, or timings.

Reg

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